Vol. 50.] ANNIVERSAR? ADDRESS OF THE PRESIDENT. 107 



some theoretical questions of extreme interest ; but it still remains 

 to be seen how far the methods which he suggests are precisely 

 those which have actually been in operation. 



General Petrology. 



In bidding farewell to the Archaean rocks we may be said to have 

 reached the base of the stratigraphical column, and at this point I 

 might, perhaps, have brought my address to a conclusion. There 

 remains, to be sure, a large amount of matter yet to be dealt with. 

 In addition to the papers relating more especially to the Funda- 

 mental Rocks — papers which are themselves largely based on 

 petrological considerations — we have had a number of communica- 

 tions in which petrology may be regarded as the chief factor. 

 Indeed, as the Fellows of the Society know very well, a ' petrological 

 night ' has been no uncommon feature at our meetings for some years 

 past. These papers may roughly be divided into two primary 

 classes, according as they relate to the British Isles or to foreign 

 countries. In the former class are papers dealing with Scotland, 

 the Lake District, Wales, Devonshire, the Lizard, and, lastly, the 

 Channel Islands, including notices of Britanny. The papers on 

 foreign subjects relate to Switzerland and the Alps, and to countries 

 so distant as Brazil and New Zealand, besides a host of papers on 

 a variety of subjects ranging from Piedmontite-schist in Japan to 

 the Tudor specimen of Eozoon and the Dwindling and Disappearance 

 of Limestones. The total number of these petrological papers exceeds 

 sixty. In order to bring the present address within a reasonable 

 compass, I must limit my remarks to papers on the British Isles 

 and their immediate vicinity, and even in this case those papers 

 which are in the main petrographic or mineralogical will be 

 omitted. Of course it is obvious that, in dealing with a subject 

 which has so many technical issues, none but a specialist could 

 hope fully to grapple with the details. It is for this reason also 

 that, instead of basing the subdivisions on philosophical grounds, 

 I have adopted, as the more simple plan, a topographical arrange- 

 ment, although this has the disadvantage of mixing the subjects in 

 an inconvenient manner. The rocks considered under this heading 

 may be of any age from Archaean upwards. 



Scotland. — There have been four papers by Prof. Judd, one by 

 Miss Gardiner, and three by the officers of the Survey. 



Prof. Judd's first two papers, on the Tertiary Volcanoes and on 



